This invention relates to surgical instruments. More particularly, this invention relates to an apparatus for automatically counting the number of times a surgical instrument has been sterilized. This invention finds particular use in endoscopic surgical instruments which are preferably disposed of after a certain number of uses.
Endoscopic surgery is widely practiced throughout the world today and its acceptance is growing rapidly. In general, endoscopic surgery involves one or more incisions made by trocars where trocar tubes are left in place so that endoscopic surgical instruments may be inserted through the tubes. A camera, lens, or other optical instrument is often inserted through a first trocar tube, while a cutter, dissector, or other surgical instrument is inserted through a second trocar tube for purposes of manipulating and/or cutting the internal organ. It is often desirable to have several trocar tubes in place at once in order to receive several surgical instruments. In this manner, an organ or tissue may be grasped with one surgical instrument, and simultaneously may be cut with another surgical instrument; all under view of the surgeon via the optical instrument in place in a trocar tube.
By 1996, it is expected that more than two million additional endosurgeries will be performed per year that, in 1990, were done via open surgery (MedPRO Month, I:12, p. 178). The advantages of endoscopic surgery are clear in that it is less invasive, less traumatic and recovery is typically quicker. As a result, many new instruments and devices for use in endosurgery are introduced every year. Most endoscopic instruments have similar configurations with a proximal handle, an actuation mechanism, and distal end effectors coupled by a tube through which the actuation mechanism extends. The end effectors take many forms such as grippers, cutters, forceps, dissectors and the like. Some endoscopic instruments are provided with a ferrule on the tube so that the tube which carries the end effectors can be rotated relative to the handle. Initially, endoscopic surgical instruments were very expensive, partly because they must be very small but still durable and reliable and the materials necessary to provide these features are expensive.
Recently, a number of "disposable" endoscopic instruments have been introduced and their use is now widely accepted. One of the advantages of disposable endoscopic instruments over reusable instruments is that because they are used only a single time, there are no sterilization problems, and no concerns about the dulling or nicking of blades or wearing of parts. However, in order to justify disposing of instruments after a single use, the instruments have to be much less expensive than the reusable tools. In order to manufacture the instruments less expensively, the disposable instruments therefore use less expensive materials. As a result, the disposable instruments are less durable than the reusable instruments, which is not of concern where the instruments are used only once. However, in order to reduce the costs of medical procedures, many hospitals and surgeons have recently started to sterilize and reuse the "disposable" endoscopic instruments. This practice can be problematic. While the disposable endoscopic instruments typically are not so fragile that they must be disposed of after a single use, clearly, they may not be used as many times as the typical stainless steel reusable instruments as they are more likely to malfunction and dull after several uses. Presently, there is no scientific mechanism available for determining how many times a medical instrument has been used, and the surgeon or the surgical staff must devise their own system to keep track of the number of times a tool has been used so that it will not be used after its useful life has expired.
Parent application Ser. No. 07/998,951 discloses an apparatus for counting the number of times a surgical device has been sterilized. The apparatus includes an indicator having sequential indicia and a heat responsive member for indicating a next one of the indicia. Mechanical, fluid mechanical and electronic versions of the invention are disclosed. In one of the mechanical versions, the indicator is a ratchet member having teeth, a direction limiting pawl, and a display surface containing indicia. A heat responsive element such as a bimetallic member engages the teeth of the ratchet and advances the ratchet each time the apparatus is subjected to the heat of sterilization. The direction limiting pawl prevents the ratchet member from moving backwards once it is advanced. A housing with a window can mask the display to indicate one of the indicia as advanced by the heat responsive element. Preferred embodiments of the mechanical version disclosed in the parent application thereto include a ring-like ratchet member with interior teeth and an exterior display surface. The number of teeth is preferably one or more less than the number of indicia so that upon advancing the ratchet member to the last indicia, it can be advanced no further. The bimetallic element is mounted inside the ring and the housing covers the outer surface of the ring. The housing may be formed from the ferrule of an endoscopic surgical tool or may be formed as part of the handle of such a tool. A disengagable locking pin is provided to prevent movement of the ratchet member during shipping and the locking pin may be coupled to packaging so that it is automatically removed when the surgical tool is removed from its packaging.
Parent application Ser. No. 07/999,228 discloses an apparatus for counting the number of times a temperature cycle occurs which includes an indicator having sequential indicia and a temperature responsive member for indicating a next one of the indicia. Again, mechanical, fluid mechanical and electronic versions of the invention are disclosed, and in the mechanical version, the indicator can be a ratchet member having teeth, a direction limiting pawl, and a display surface containing indicia. A temperature responsive element such as a bimetallic member engages the teeth of the ratchet and advances the ratchet each time the apparatus is subjected to a preset temperature cycle. A housing with a window masks the display to indicate one of the indicia as advanced by the temperature responsive element. Preferred embodiments of this mechanical version include a ring-like ratchet. member with interior teeth and an exterior display surface The number of teeth is preferably one or more less than the number of indicia so that upon advancing the ratchet member to the last indicia, it can be advanced no further. The bimetallic element is mounted inside the ring and the housing covers the outer surface of the ring. A disengagable locking pin is provided to prevent movement of the ratchet member until activated.
The mechanical embodiments of the parent applications have a few disadvantages when miniaturized for use, for example, with endoscopic surgical instruments. First, the direction limiting pawl which is used to prevent backward movement of the ratchet member must be very small, e.g., approximately 0.15 inches long with a diameter of approximately 0.01 inches. Moreover, in an exemplary embodiment used with endoscopic surgical instruments, the depth of ratchet teeth is only approximately 0.015 inches. Given the relative criticality of alignment necessary to permit accurate functioning of the counter, these dimensions make the direction limiting pawl difficult and/or expensive to manufacture in large amounts. While, an escapement mechanism was suggested as an alternative to the direction limiting pawl when used with a rotating ratchet member, because the escapement mechanism would be driven by the free end of the bimetallic member, realization of this embodiment would also be difficult and/or expensive in large amounts.
Another minor disadvantage of the mechanical embodiments of the parent applications involved the use of disengagable locking pins which was used to prevent activation of the counter. It was recognized, however, that by leaving the pin engaged in the counter during sterilization, the counter mechanism could be defeated.
Patent application Ser. No. 08/016,596 discloses endoscopic instruments having a reusable portion (the handle and actuating means) and a disposable portion (the tube, push rod and end effectors). The two portions can be coupled and uncoupled so that the disposable portion may be disposed of while the reusable portion may be reused with a new disposable portion. As with the completely disposable endoscopic instruments, some surgeons may choose to reuse the disposable portion a few times before replacing it. In these situations, it is important to alert the surgeon and/or the surgical staff before the disposable portion has been used too many times. The counting mechanisms described in the other parent applications do not specifically disclose how they can be used with endoscopic instruments having separable disposable and reusable parts.